The idea was to be able to have the water line on the camera frame when it goes in and out of the water, to see above and under water simultaneously, so, for that to happen and actually make sense i first had to have a place. I ended up digging a swimming pool from Turbosquid, plus some other meshes from elsewhere and put them together in a scene where it could make sense to have this particular effect. This is what i ended up with. Not perfect or finished but still, it looks nice.